You'll see a lot of hype on here regarding the Seth Mos. A lot of this hype is indeed justified, they are a solid glove. However after putting close to 100 days on mine, I think I can provide some kind of review on the glove's performance. I've used the glove inbounds and out in BC, Europe and back home here in Scotland.
When I got the Seths I was coming off a pair of fabric shell Dakine gloves. So when I first put on a pair of the Seth Mos I instantly noticed the warmth and improved waterproofing. I have from day one noticed a slight drop off in dexterity with the Seth Mos compared to other gloves, due mostly to the protection on the knuckles. Whilst the waterproofing is pretty optimal, it does require intermittent attention with leather balm, if you can keep on top of this then the waterproofing stays pretty prime. Unfortunately whilst they are good at keeping water out, they can get pretty sweaty inside and once they get like this, I've found they tend to stay like this for the rest of the day. Although at times they feel too warm, I've often found them to not be warm enough in the depths of winter. As soon as it gets below about -6/-7c (20F) I found the Seth Mos to simply not be up to the task, and if there is precipitation the tips of the fingers on the outside will start to freeze up. Whilst the leather of the glove (goat on the palm and cow hide on the back of the hide) stays intact for a long period of time, I've found on my pair after about 85 days of use the stitching has started to detiriorate and so, even with careful attention to leather balming I'm now finding myself fairly damp whenever there's precipitation. As a resuly they now sit at the bottom of my pack as a back up pair. Just one final thing to watch out for with these is that where the liner of the glove is stitched only to the wrist of the glove, if you take you hand out of the glove too quickly or without an inner glove on then you can pull the glove's liner out of place and get it tangled.
Whilst these gloves certainly are superior to a great number of other gloves on the market, I wouldn't go so far as to say they are the best. Perhaps if you live somewhere mild and dry and don't do a huge amount of hiking, then these might just be the glove for you.